Photothermal Test Camera Provided With An Optical Device For Extending A Laser Beam Section

Abstract

The inventive photothermal test camera ( 16 ) is provided with a laser beam ( 4 ) shaping system ( 22 ) comprising a device ( 40 ) for extending the laser beam section in such a way that a heating area ( 2 ) extended in a direction (D) is formed on the surface of a testable piece ( 1 ), an array ( 8 ) of infrared sensors ( 10 ) for detecting a infrared radiation transmitted by a detection area ( 3 ) on the surface ( 1 a ) of the piece ( 1 ) with respect to the heating area ( 2 ) and a unit ( 46 ) for processing signals transmitted by the infrared sensors ( 10 ) in such a way that a thermographic image of the piece ( 1 ) surface ( 1 a ) is produced by scanning said surface ( 1 a ) with the aid of the heating area ( 2 ). An extending device ( 40 ) is embodied in the form of an optical device. Said invention can be used for non-destructive testing.

1 . Camera ( 16 ) for photothermal examination, of the type that comprises:
 a system ( 22 ) for shaping a laser beam ( 4 ) comprising a device ( 40 ) for extending the section of the beam to form a heating area ( 2 ) extended in one direction (D), on the surface of an item ( 1 ) to be examined,   a matrix ( 8 ) of infrared detectors ( 10 ) to detect infrared radiation emitted by a detection area ( 3 ) on the surface ( 1   a ) of the item ( 1 ), and   a unit ( 46 ) for processing signals supplied by the infrared detectors ( 10 ) to construct a thermographic image of the surface ( 1   a ) of the item ( 1 ) by scanning the surface ( 1   a ) through the heating area ( 2 ),   wherein the extension device ( 40 ) is an optical device.   
   
   
       2 . Camera according to  claim 1 , wherein the optical device ( 40 ) comprises a lens ( 42 ) designed to be passed through by the laser beam ( 4 ). 
   
   
       3 . Camera according to  claim 1 , wherein the optical device ( 40 ) comprises a mirror ( 56 ) designed to reflect the laser beam ( 4 ). 
   
   
       4 . Camera according to  claim 1 , wherein the shaping system ( 22 ) comprises a device ( 40 ) for homogenising the power of the laser beam ( 4 ) along the heating area ( 2 ). 
   
   
       5 . Camera according to  claim 4 , wherein the power homogenisation device is formed by the laser beam section extension device ( 40 ). 
   
   
       6 . Camera according to  claim 2 , wherein one face ( 44 ) of the lens ( 42 ) has a profile suitable for homogenising the power of the laser beam ( 4 ) along the heating area ( 2 ). 
   
   
       7 . Camera according to  claim 3 , wherein one reflecting face ( 58 ) of the mirror ( 56 ) has a profile suitable for homogenising the power of the laser radiation ( 4 ) along the heating area ( 2 ). 
   
   
       8 . Camera according to  claim 5 , wherein the homogenisation device ( 40 ) is a device for forming a line by causing the laser beam ( 4 ) to move perpendicularly to its propagation direction. 
   
   
       9 . Camera according to  claim 8 , wherein the device ( 40 ) comprises an acousto-optical cell ( 60 ). 
   
   
       10 . Camera according to  claim 8 , wherein the homogenisation device ( 40 ) comprises an oscillating mirror ( 64 ). 
   
   
       11 . Camera according to  claim 5 , wherein the homogenisation device ( 40 ) comprises a bundle ( 66 ) of optical fibres ( 68 ) the upstream ends ( 70 ) of which receive the laser beam ( 4 ) and the downstream ends of which are arranged along a line to create the extended heating area ( 2 ). 
   
   
       12 . Camera according to  claim 1 , wherein it comprises a system ( 52 ,  54 ) for mechanical adjustment of a space d between the extended heating area ( 2 ) and the detection area ( 3 ). 
   
   
       13 . Camera according to  claim 12 , wherein it comprises a box ( 18 ), and in that the mechanical adjustment system comprises a device ( 52 ) for moving the matrix ( 8 ) of infrared detectors ( 10 ) in relation to the box ( 18 ). 
   
   
       14 . Camera according to  claim 12 , wherein it comprises a box ( 18 ), and in that the mechanical adjustment system comprises a device ( 54 ) for moving the shaping system ( 22 ) in relation to the box ( 18 ). 
   
   
       15 . Camera according to  claim 13 , wherein the movement device ( 52 ,  54 ) comprises a linear motor. 
   
   
       16 . Camera according to  claim 13 , wherein in that the movement device ( 52 ,  54 ) comprises a piezoelectric linear actuator. 
   
   
       17 . Camera according to  claim 13 , wherein the movement device ( 52 ,  54 ) comprises a rotary motor and a mechanism for transforming a rotary movement into a translation movement. 
   
   
       18 . Camera according to  claim 1 , wherein in that it comprises a filter blade ( 32 ) to reflect the laser beam ( 4 ) and transmit the infrared radiation ( 5 ) radiated by the detection area ( 3 ) towards the matrix ( 8 ) of infrared detectors ( 10 ). 
   
   
       19 . Camera according to  claim 18 , wherein the blade comprises at least one material chosen from the list made up of CaF 2 , MgF 2 , Al 2 O 3 , BaF 2 , Ge, ZnSe, ZnS FLIR, multispectral ZnS, MgO and SrF 2 . 
   
   
       20 . Camera according to  claim 1 , wherein it comprises a system for scanning the surface ( 1   a ) of the item ( 1 ) through the heating area ( 2 ). 
   
   
       21 . Camera according to  claim 1 , wherein the processing unit ( 46 ) is suitable for adjusting a space (d) between the heating area ( 2 ) and the detection area ( 3 ) by selecting a row ( 12 ) of infrared detectors ( 10 ) in a detection matrix ( 8 ). 
   
   
       22 . Camera according to  claim 1 , wherein the processing unit ( 46 ) is suitable for the independent processing of signals provided by each of the infrared detectors ( 10 ) of the matrix ( 8 .) 
   
   
       23 . Camera according to  claim 1 , wherein it comprises a laser source ( 34 ). 
   
   
       24 . Camera according to  claim 1 , wherein it comprises connection means ( 36 ) to a laser source ( 34 ) that does not form part of the camera.